I don't know: from earlier researches, it seems Sparrow is based on LibEtPan which is open-source: - http://www.etpan.org/libetpan/index.html http://www.etpan.

I don't know: from earlier researches, it seems Sparrow is based on LibEtPan which is open-source: - http://www.etpan.org/libetpan/index.html http://www.etpan.org/libetpan/index.html - https://twitter.com/sparrow/status/6396505883676672 https://twitter.com/sparrow/status/6396505883676672